Update README.md

Author: SidneyAllen

README.md

@@ -20,13 +20,17 @@ Official python SDK for Xero API generated by OpenAPI spec for oAuth 2
 
     * [Accounting API](https://developer.xero.com/documentation/api/api-overview)
     * [Assets API](https://developer.xero.com/documentation/assets-api/overview)
+    * [Files API](https://developer.xero.com/documentation/files-api/overview-files)
+    * [Payroll API (AU)](https://developer.xero.com/documentation/payroll-api/overview)
+    * [Payroll API (NZ)](https://developer.xero.com/documentation/payroll-api-nz/overview)
+    * [Payroll API (UK)](https://developer.xero.com/documentation/payroll-api-uk/overview)
     * [Projects API](https://developer.xero.com/documentation/projects/overview-projects)
-    * [AU Payroll API](https://developer.xero.com/documentation/payroll-api/overview)
-    * [UK Payroll API](https://developer.xero.com/documentation/payroll-api-uk/overview)
-    * [NZ Payroll API](https://developer.xero.com/documentation/payroll-api-nz/overview)
-
+    
 * Error handling for ease of use.
 
+## SDK Documentation
+* [Accounting](https://xeroapi.github.io/xero-python/v1/accounting/index.html)
+
 ## Starter Project
 We've created [xero-python-outh2-starter](https://github.com/XeroAPI/xero-python-oauth2-starter) a project to demonstrate how to use this SDK.